I see a bunch of elbow grease turning that bike into one clean machine.
Being in such good condition its odd those parts were replaced.
Those bikes had a style/look all too their own , definitely a nice find that any enthusiast would be proud too have it in their collection.
here's few pics of my old trike that might help you out.
I wouldn't put a clutch on one of these trikes probably wouldn't last or work so well.